1. Field of the Invention
The present invention relates to a communication system in an endoscope system including an endoscope loaded with a CMOS sensor as an image pickup device.
2. Description of the Related Art
Conventionally, as a general-purpose serial connection system for connecting a plurality of elements by communication, a serial communication standard referred to as so-called I2C (inter-integrated circuit) is known.
The I2C is a synchronous type serial communication standard of performing communication by two bidirectional open collector signal lines (serial data SDA and serial clock SCL) pulled up by a resistor, and write to a specified device and read are performed using the SDA and SCL. The SDA and SCL are both bus signals and the plurality of elements are connected by the bus in the I2C.
Then, in the I2C, a master that requests read and write of data utilizing the bus signals of the SDA and SCL and a slave that receives and sends out the data according to requests of the master are provided, and the plurality of slaves can be connected to the bus further. In addition, the master selects a slave by specifying an individually determined address of the slave and then communicates with the slave.
On the other hand, conventionally, an endoscope including an image pickup device has been widely used in a medical field and an industrial field. In addition, a technique of configuring an endoscope system in which a signal processing device referred to as a processor is freely attachably and detachably connected to the endoscope and bears various kinds of signal processing relating to the endoscope is also known.
In addition, in recent years, an endoscope adopting a CMOS sensor as an image pickup device has been also proposed. The CMOS sensor of the kind includes an A/D conversion portion together with an image pickup portion inside a sensor chip of the CMOS sensor, and an output signal as the sensor is a digital signal.
Then, in the endoscope system including the endoscope adopting the CMOS sensor of the kind, a technique of performing communication control between the CMOS sensor and a processor which is a signal processing portion by the I2C described above is known (Japanese Patent No. 5356632).
Now, in a case of the endoscope system adopting the CMOS sensor at an endoscope distal end, which performs the communication control by the I2C described above, a configuration that the CMOS sensor is one of the slaves and the master is mounted on the processor is conceivable.
In the case of such an endoscope system, the CMOS sensor disposed at an endoscope distal end portion and the processor are connected by a cable having a length of several meters, however, it means that the CMOS sensor which is one of the slaves and the processor which is the master are connected by the cable of several meters.